This invention is generally directed to toner compositions, and the use of these compositions in electrostatographic imaging systems. More specifically, the present invention is directed to colored toner resins which can be selected for the formulation of colored toner and developer compositions where leaching or bleeding of the colorants is substantially eliminated. Without leaching there are enabled toner compositions that retain their color fidelity or intensity over extended time periods. Also, the dyed toner and developer compositions of the present invention are useful in various electrostatographic imaging systems, particularly colored imaging systems, having incorporated therein as the photoresponsive member a layered imaging device which is negatively charged.
Toner and developer compositions including colored developer compositions are well known. These compositions usually contain toner particles consisting of a resin and colorants, and carrier particles. With regard to colored developer compositions, the colorants are usually selected from cyan dyes or pigments, magenta dyes or pigments, yellow dyes or pigments, and mixtures thereof. There is thus disclosed in U.S. Pat. No. 3,844,815 colored developer compositions containing as the yellow pigment Foron Yellow, while U.S. Pat. No. 4,035,310 discloses colored toner compositions comprised of pigment Yellow 97; and carrier particles generally comprised of steel coated with various polymeric resinous substances.
Also, it is known that the prime advantage of selecting organic dyes instead of pigments for color toner compositions resides in the provisions of increased color fidelity as the dyes can be molecularly dispersed in the toner resins. To obtain a homogeneous dispersion, however, it is generally necessary to build into these molecules certain substituents for enhancing their compatibility with the toner resin. Unless the dye molecules are fully compatible with the toner resins, they have a tendency to aggregate with time, especially when subjected to heat, pressure and humidity thereby resulting in a loss of color fidelity. Additionally, the low molecular weights of the dye molecules causes a high lability, or mobility of the dye molecules in the toner resin resulting in undesirable bleeding of the dyes.
Several prior art patents also disclose the incorporation into toner compositions as separate components, charge enhancing additives primarily for the purpose of imparting a positive charge to the toner resin particles. There is thus disclosed in U.S. Pat. No. 4,298,672 positively charged toner compositions containing resin particles and pigment particles, and as a charge enhancing additive alkyl pyridinium compounds and their hydrates of the formula as detailed in column 3, beginning at line 14. Examples of alkyl pyridinium compounds disclosed include cetyl pyridinium chloride. Moreover, there is disclosed in U.S. Pat. No. 4,338,390 positively charged toner compositions having incorporated therein as charge enhancing additives various organic sulfate and sulfonate compositions, including stearyl dimethyl phenethylammonium paratoluene sulfonate. Further, in U.S. Pat. No. 3,893,935 there is described the use of quaternary ammonium salts as charge control agents for electrostatic toner compositions.
Additionally, there are disclosed in the prior art colored toner and developer compositions containing as charge enhancing additives para-halophenylcarboxylic acids and the salts thereof. More specifically, there are disclosed in this patent positively charged toner compositions containing resin particles; dye particles such as cyan, magenta, or yellow dyes; and as a charge enhancing additive in an amount of from about 0.1 percent by weight to about 10 percent by weight parahalophenylcarboxylic acids, and the salts thereof, including 4-fluorobenzoic acid, 4-chlorobenzoic acid, and 4-bromobenzoic acid.
Other prior art includes U.S. Pat. No. 3,699,135 which discloses polymeric dyes prepared by the copolymerization of a specific silane with a derivative of an anthraquinone containing two aliphatic hydroxy groups; and U.S. Pat. Nos. 3,232,691; 3,549,304; and 4,101,269. These references appear to disclose that the functional group formed on the chromophore enters into the polymerization reaction with the monomer leaving the chromophore as a pendant moiety in the polymer structure. Of background interest pertaining to the chemical incorporation of chromophores into polymers there were selected as prior art U.S. Pat. Nos. 3,027,362; 3,117,957; 3,337,288; 3,344,098; 3,462,388; 3,467,642; 3,639,243; 3,852,208; 4,051,183; 4,194,877; 4,217,406; 4,339,237; and 4,397,651.
Although the above described toner and developer compositions are suitable for their intended purposes, there continues to be a need for new compositions. Specifically, there continues to be a need for colored toner compositions wherein dye aggregation and dye bleeding are eliminated. Also, there is a need for colored toner compositions which retain their color fidelity for extended time periods. There is also a specific need for colored toner compositions wherein the colorants exhibit no tendency to leach, bleed, or sublime. Further, there remains a need for colored toner compositions whose colorants are uniformly dispersed thus imparting greater clarity and brightness to the resultant electrographic prints. Moreover, there is a need for toner compositions wherein the toner resin particles are intrinsically colored. Further, there is a need for colored toner compositions wherein the dye chromophores are covalently linked to the backbone of the polymer resin thereby avoiding the prior art problems of dye bleeding and aggregation normally associated with the dye-in-polymer compositions. Additionally, there is a need for processes that enable the simple preparation of intrinsically colored toner compositions.